Stumble Start Condition
Thread Starter
Melting Slicks
Joined: Nov 2006
Posts: 2,001
Likes: 42
From: Ventura, California
Stumble Start Condition
I have a stumble start condition that only developed recently. I have about 1000 miles on the new motor. When it was new it would always fire immediately, when hot or cold. Everything was new at the time of the motor, battery, starter, etc. When the motor is hot/ up to operating temperature, it fires very quickly, just like it did when cold when the motor was new. However if I leave it overnight, it kinda stutters/ stumbles but still starts quickly, just not cleanly. I have a fuel pressure gauge on the car, with the key-on, pressure goes to 58psi, then after a second or so it goes down to 50psi, which I think is normal. It doesn't crank forever like when you have a bad fuel pump check valve, it fires pretty much right away, but stumbles on its way to idle, if that makes sense.
I did let the battery die a few weeks back, but it doesn't make sense that it starts fast when the motor is hot. Would a loose timing chain affect start-up time? I wonder if the Bosch aftermarket starter is having trouble keeping up with the compression.
I did let the battery die a few weeks back, but it doesn't make sense that it starts fast when the motor is hot. Would a loose timing chain affect start-up time? I wonder if the Bosch aftermarket starter is having trouble keeping up with the compression.
Thread Starter
Melting Slicks
Joined: Nov 2006
Posts: 2,001
Likes: 42
From: Ventura, California
It's not the pump, fuel pressure should bleed off gradually otherwise what would be the point of priming the fuel pump? It could be the injectors leaking fuel into the cylinders possibly.
Thread Starter
Melting Slicks
Joined: Nov 2006
Posts: 2,001
Likes: 42
From: Ventura, California
I pulled the rail and had a helper prime the pump, injector #8 had a little squirt which would put raw fuel into the cylinder before startup.
Sending the injectors in for cleaning and pressure testing.
Advanced
Joined: Jun 2015
Posts: 85
Likes: 4
From: Richmond Hill
It almost sounds like the M.A.F, GM"s 3.8 acted that way with cold morning start-ups, I'm not sold on leaking injectors cause that would be a long crank issue then fire up. Maybe a lazy I.A.C ? clean throttle body lately?
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